Biofluid Biomarkers in Traumatic Brain Injury: A Systematic Scoping Review

Fluid biomarkers of chronic traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of long-term disability across the world. Evidence for the usefulness of imaging and fluid biomarkers to predict outcomes and screen for the need to monitor complications in the acute stage is steadily increasing. Still, many people experience symptoms such as fatigue and cognitive and motor dysfunction in the chronic phase of TBI, where objective assessments for brain injury are lacking. Consensus criteria for traumatic encephalopathy syndrome, a clinical syndrome possibly associated with the neurodegenerative disease chronic traumatic encephalopathy, which is commonly associated with sports concussion, have been defined only recently. However, these criteria do not fit all individuals living with chronic consequences of TBI. The pathophysiology of chronic TBI shares many similarities with other neurodegenerative and neuroinflammatory conditions, such as Alzheimer disease. As with Alzheimer disease, advancements in fluid biomarkers represent one of the most promising paths for unravelling the chain of pathophysiological events to enable discrimination between these conditions and, with time, provide prediction modelling and therapeutic end points. This Review summarizes fluid biomarker findings in the chronic phase of TBI (≥6 months after injury) that demonstrate the involvement of inflammation, glial biology and neurodegeneration in the long-term complications of TBI. We explore how the biomarkers associate with outcome and imaging findings and aim to establish mechanistic differences in biomarker patterns between types of chronic TBI and other neurodegenerative conditions. Finally, current limitations and areas of priority for future fluid biomarker research are highlighted.

Systemic and cerebro-cardiac biomarkers following traumatic brain injury: an interim analysis of randomized controlled clinical trial of early administration of beta blockers

This is an interim analysis of the Beta-blocker (Propranolol) use in traumatic brain injury (TBI) based on the high-sensitive troponin status (BBTBBT) study. The BBTBBT is an ongoing double-blind placebo-controlled randomized clinical trial with a target sample size of 771 patients with TBI. We sought, after attaining 50% of the sample size, to explore the impact of early administration of beta-blockers (BBs) on the adrenergic surge, pro-inflammatory cytokines, and the TBI biomarkers linked to the status of high-sensitivity troponin T (HsTnT). Patients were stratified based on the severity of TBI using the Glasgow coma scale (GCS) and HsTnT status (positive vs negative) before randomization. Patients with positive HsTnT (non-randomized) received propranolol (Group-1; n = 110), and those with negative test were randomized to receive propranolol (Group-2; n = 129) or placebo (Group-3; n = 111). Propranolol was administered within 24 h of injury for 6 days, guided by the heart rate (> 60 bpm), systolic blood pressure (≥ 100 mmHg), or mean arterial pressure (> 70 mmHg). Luminex and ELISA-based immunoassays were used to quantify the serum levels of pro-inflammatory cytokines (Interleukin (IL)-1β, IL-6, IL-8, and IL-18), TBI biomarkers [S100B, Neuron-Specific Enolase (NSE), and epinephrine]. Three hundred and fifty patients with comparable age (mean 34.8 ± 9.9 years) and gender were enrolled in the interim analysis. Group 1 had significantly higher baseline levels of IL-6, IL-1B, S100B, lactate, and base deficit than the randomized groups (p = 0.001). Group 1 showed a significant temporal reduction in serum IL-6, IL-1β, epinephrine, and NSE levels from baseline to 48 h post-injury (p = 0.001). Patients with severe head injuries had higher baseline levels of IL-6, IL-1B, S100B, and HsTnT than mild and moderate TBI (p = 0.01). HsTnT levels significantly correlated with the Injury Severity Score (ISS) (r = 0.275, p = 0.001), GCS (r = - 0.125, p = 0.02), and serum S100B (r = 0.205, p = 0.001). Early Propranolol administration showed a significant reduction in cytokine levels and TBI biomarkers from baseline to 48 h post-injury, particularly among patients with positive HsTnT, indicating the potential role in modulating inflammation post-TBI.Trial registration: ClinicalTrials.gov NCT04508244. It was registered first on 11/08/2020. Recruitment started on 29 December 2020 and is ongoing. The study was partly presented at the 23rd European Congress of Trauma and Emergency Surgery (ECTES), April 28-30, 2024, in Estoril, Lisbon, Portugal.

[Current Aspects of Intensive Medical Care for Traumatic Brain Injury - Part 2 - Secondary Treatment Strategies, Long-term Outcome, Neuroprognostics and Chronification]

This two-part article deals with the intensive medical care of traumatic brain injury. Part 1 addresses the primary treatment strategy, haemodynamic management and multimodal monitoring, Part 2 secondary treatment strategies, long-term outcome, neuroprognostics and chronification. Traumatic brain injury is a complex clinical entity with a high mortality rate. The primary aim is to maintain homeostasis based on physiological targeted values. In addition, further therapy must be geared towards intracranial pressure. In addition to this, there are other monitoring options that appear sensible from a pathophysiological point of view with appropriate therapy adjustment. However, there is still a lack of data on their effectiveness. A further aspect is the inflammation of the cerebrum with the "cross-talk" of the organs, which has a significant influence on further intensive medical care.

Admission S100B fails as neuro-marker but is a good predictor for intrahospital mortality in major trauma patients

BACKGROUND

S100 B is an extensively studied neuro-trauma marker, but its specificity and subsequently interpretation in major trauma patients might be limited, since extracerebral injuries are known to increase serum levels. Thus, we evaluated the potential role of S100B in the assessment of severe traumatic brain injury (TBI) in multiple injured patients upon emergency room (ER) admission and the first days of intensive care unit (ICU) stay.

METHODS

Retrospective study employing trauma registry data derived from a level 1 trauma center. Four cohorts of patients were grouped: isolated TBI (iTBI), polytrauma patients with TBI (PT + TBI), polytrauma patients without TBI (PT-TBI) and patients without polytrauma or TBI (control). S100B-serum levels were assessed immediately after admission in the emergency room and during the subsequent ICU stay. Values were correlated with injury severity score (ISS), Glasgow Coma Score (GCS) and in-hospital mortality.

RESULTS

780 predominantly male patients (76 %) with a median age of 48 (30-63) and a median ISS of 24 (17-30) were enrolled in the study. Admission S100B correlated with ISS and TBI severity defined by the GCS (both p < 0.0001) but not with head abbreviated injury score (AIS) (p = 0.38). Compared with survivors, non-survivors had significantly higher median S100B levels in the ER (6.14 μg/L vs. 2.06 μg/L; p < 0.0001) and at ICU-day 1 (0.69 μg/L vs. 0.17 μg/L; p < 0.0001). S100B in the ER predicted mortality with an area under curve (AUC) of 0.77 (95 % CI 0,70-0,83, p < 0.0001), vs. 0.86 at ICU-day 1 (95 % CI 0,80-0,91, p < 0.0001).

CONCLUSION

In conclusion, S100B is a valid biomarker for prediction of mortality in major trauma patients with a higher accuracy when assessed at the first day of ICU stay vs. immediately after ER admission. Since S100B did not correlate with pathologic TBI findings in multiple injured patients, it failed as predictive neuro-marker because extracerebral injuries demonstrated a higher influence on admission levels than neurotrauma. Although S100B levels are indicative for injury severity they should be interpreted with caution in polytrauma patients.

Measuring Salivary Cortisol to Assess the Effect of Natural Environments on Stress Level in Acute Patients With Severe Brain Injuries: An Exploratory Study

BACKGROUND

Salivary cortisol is a safe and non-invasive measure of hypothalamic-pituitary-adrenal axis function and is used as a biomarker of the human stress response. Natural environments are recognized to contribute to help reduce the effect of stress.

OBJECTIVE

To determine the feasibility of a salivary cortisol collection protocol for acute severely brain-injured patients, and to explore the influence of exposure to natural settings on salivary cortisol concentration as an index of stress level.

METHODS

An exploratory study on 17 acute patients with severe brain injury was performed. We collected salivary samples in a closed hospital ward and a therapeutic garden at the start of the session and after 30 minutes of rest time. Physiological parameters, level of communication, and subjective well-being were also assessed.

RESULTS

The primary objectives regarding the feasibility of the protocol were met overall. We found no significant differences in cortisol values when including the whole population. However, cortisol values were significantly higher in the indoor environment in patients with communication attempts.

CONCLUSIONS

A salivary collection protocol with brain-injured patients in the acute phase is feasible and safe, and this type of measurement could pave the way for future research supporting the benefits of nature as an additional resource in their neurorehabilitation.

Association of Brain Injury Biomarkers and Circulatory Shock Following Moderate-Severe Traumatic Brain Injury: A TRACK-TBI Study

INTRODUCTION

Early circulatory shock following traumatic brain injury (TBI) is a multifactorial process; however, the impact of brain injury biomarkers on the risk of shock has not been evaluated. We examined the association between neuronal injury biomarker levels and the development of circulatory shock following moderate-severe TBI.

METHODS

In this retrospective cohort study, we examined adults with moderate-severe TBI (Glasgow Coma Scale score <13) enrolled in the TRACK-TBI study, an 18-center prospective TBI cohort study. The exposures were day-1 levels of neuronal injury biomarkers (glial fibrillary acidic protein, ubiquitin C-terminal hydrolase-L1 [UCH-L1], S100 calcium-binding protein B [S100B], neuron-specific enolase), and of an inflammatory biomarker (high-sensitivity C-reactive protein). The primary outcome was the development of circulatory shock, defined as cardiovascular Sequential Organ Failure Assessment Score ≥2 within 72 hours of admission. Association between day-1 biomarker levels and the development of circulatory shock was assessed with regression analysis.

RESULTS

The study included 392 subjects, with a mean age of 40 years; 314 (80%) were male and 165 (42%) developed circulatory shock. Median (interquartile range) day-1 levels of UCH-L1 (994.8 [518.7 to 1988.2] pg/mL vs. 548.1 [280.2 to 1151.9] pg/mL; P <0.0001) and S100B (0.47 μg/mL [0.25 to 0.88] vs. 0.27 [0.16 to 0.46] μg/mL; P <0.0001) were elevated in those who developed early circulatory shock compared with those who did not. In multivariable regression, there were associations between levels of both UCH-L1 (odds ratio, 1.63 [95% confidence interval, 1.25-2.12]; P <0.0005) and S100B (odds ratio, 1.73 [95% confidence interval 1.27-2.36]; P <0.0005) with the development of circulatory shock.

CONCLUSION

Neuronal injury biomarkers may provide the improved mechanistic understanding and possibly early identification of patients at risk for early circulatory shock following moderate-severe TBI.

Repeated Low-Level Blast Exposure Alters Urinary and Serum Metabolites

Repeated exposure to low-level blast overpressures can produce biological changes and clinical sequelae that resemble mild traumatic brain injury (TBI). While recent efforts have revealed several protein biomarkers for axonal injury during repetitive blast exposure, this study aims to explore potential small molecule biomarkers of brain injury during repeated blast exposure. This study evaluated a panel of ten small molecule metabolites involved in neurotransmission, oxidative stress, and energy metabolism in the urine and serum of military personnel (n = 27) conducting breacher training with repeated exposure to low-level blasts. The metabolites were analyzed using HPLC-tandem mass spectrometry, and the Wilcoxon signed-rank test was used for statistical analysis to compare the levels of pre-blast and post-blast exposures. Urinary levels of homovanillic acid (p < 0.0001), linoleic acid (p = 0.0030), glutamate (p = 0.0027), and serum N-acetylaspartic acid (p = 0.0006) were found to be significantly altered following repeated blast exposure. Homovanillic acid concentration decreased continuously with subsequent repeat exposure. These results suggest that repeated low-level blast exposures can produce measurable changes in urine and serum metabolites that may aid in identifying individuals at increased risk of sustaining a TBI. Larger clinical studies are needed to extend the generalizability of these findings.

Central role for neurally dysregulated IL-17A in dynamic networks of systemic and local inflammation in combat casualties

Dynamic Network Analysis (DyNA) and Dynamic Hypergraphs (DyHyp) were used to define protein-level inflammatory networks at the local (wound effluent) and systemic circulation (serum) levels from 140 active-duty, injured service members (59 with TBI and 81 non-TBI). Interleukin (IL)-17A was the only biomarker elevated significantly in both serum and effluent in TBI vs. non-TBI casualties, and the mediator with the most DyNA connections in TBI wounds. DyNA combining serum and effluent data to define cross-compartment correlations suggested that IL-17A bridges local and systemic circulation at late time points. DyHyp suggested that systemic IL-17A upregulation in TBI patients was associated with tumor necrosis factor-α, while IL-17A downregulation in non-TBI patients was associated with interferon-γ. Correlation analysis suggested differential upregulation of pathogenic Th17 cells, non-pathogenic Th17 cells, and memory/effector T cells. This was associated with reduced procalcitonin in both effluent and serum of TBI patients, in support of an antibacterial effect of Th17 cells in TBI patients. Dysregulation of Th17 responses following TBI may drive cross-compartment inflammation following combat injury, counteracting wound infection at the cost of elevated systemic inflammation.

Diagnostic performance of S100B as a rule-out test for intracranial pathology in head-injured patients presenting to the emergency department who meet NICE Head Injury Guideline criteria for CT-head scan

BACKGROUND

Traumatic brain injury is a common ED presentation. CT-head utilisation is escalating, exacerbating resource pressure in the ED. The biomarker S100B could assist clinicians with CT-head decisions by excluding intracranial pathology. Diagnostic performance of S100B was assessed in patients meeting National Institute of Health and Clinical Excellence Head Injury Guideline (NICE HIG) criteria for CT-head within 6 and 24 hours of injury.

METHODS

This multicentre prospective observational study included adult patients presenting to the ED with head injuries between May 2020 and June 2021. Informed consent was obtained from patients meeting NICE HIG CT-head criteria. A venous blood sample was collected and serum was tested for S100B using a Cobas Elecsys-S100 module; >0.1 µg/mL was the threshold used to indicate a positive test. Intracranial pathology reported on CT-head scan by the duty radiologist was used as the reference standard to review diagnostic performance.

RESULTS

This study included 265 patients of whom 35 (13.2%) had positive CT-head findings. Within 6 hours of injury, sensitivity of S100B was 93.8% (95% CI 69.8% to 99.8%) and specificity was 30.8% (22.6% to 40.0%). Negative predictive value (NPV) was 97.3% (95% CI 84.2% to 99.6%) and area under the curve (AUC) was 0.73 (95% CI 0.61 to 0.85; p=0.003). Within 24 hours of injury, sensitivity was 82.9% (95% CI 66.4% to 93.44%) and specificity was 43.0% (95% CI 36.6% to 49.7%). NPV was 94.29% (95% CI 88.7% to 97.2%) and AUC was 0.65 (95% CI 0.56 to 0.74; p=0.046). Theoretically, use of S100B as a rule-out test would have reduced CT-head scans by 27.1% (95% CI 18.9% to 36.8%) within 6 hours and 37.4% (95% CI 32.0% to 47.2%) within 24 hours. The risk of missing a significant injury with this approach would have been 0.75% (95% CI 0.0% to 2.2%) within 6 hours and 2.3% (95% CI 0.5% to 4.1%) within 24 hours.

CONCLUSION

Within 6 hours of injury, S100B performed well as a diagnostic test to exclude significant intracranial pathology in low-risk patients presenting with head injury. In theory, if used in addition to NICE HIGs, CT-head rates could reduce by one-quarter with a potential miss rate of <1%.

Review: Emerging Eye-Based Diagnostic Technologies for Traumatic Brain Injury

The study of ocular manifestations of neurodegenerative disorders, Oculomics, is a growing field of investigation for early diagnostics, enabling structural and chemical biomarkers to be monitored overtime to predict prognosis. Traumatic brain injury (TBI) triggers a cascade of events harmful to the brain, which can lead to neurodegeneration. TBI, termed the "silent epidemic" is becoming a leading cause of death and disability worldwide. There is currently no effective diagnostic tool for TBI, and yet, early-intervention is known to considerably shorten hospital stays, improve outcomes, fasten neurological recovery and lower mortality rates, highlighting the unmet need for techniques capable of rapid and accurate point-of-care diagnostics, implemented in the earliest stages. This review focuses on the latest advances in the main neuropathophysiological responses and the achievements and shortfalls of TBI diagnostic methods. Validated and emerging TBI-indicative biomarkers are outlined and linked to ocular neuro-disorders. Methods detecting structural and chemical ocular responses to TBI are categorised along with prospective chemical and physical sensing techniques. Particular attention is drawn to the potential of Raman spectroscopy as a non-invasive sensing of neurological molecular signatures in the ocular projections of the brain, laying the platform for the first tangible path towards alternative point-of-care diagnostic technologies for TBI.

Mass Spectrometry-Based Approaches for Clinical Biomarker Discovery in Traumatic Brain Injury

Purpose of Review

Precision treatments to address the multifaceted pathophysiology of traumatic brain injury (TBI) are desperately needed, which has led to the intense study of fluid-based protein biomarkers in TBI. Mass Spectrometry (MS) is increasingly being applied to biomarker discovery and quantification in neurological disease to explore the proteome, allowing for more flexibility in biomarker discovery than commonly encountered antibody-based assays. In this narrative review, we will provide specific examples of how MS technology has advanced translational research in traumatic brain injury (TBI) focusing on clinical studies, and looking ahead to promising emerging applications of MS to the field of Neurocritical Care.

Recent Findings

Proteomic biomarker discovery using MS technology in human subjects has included the full range of injury severity in TBI, though critically ill patients can offer more options to biofluids given the need for invasive monitoring. Blood, urine, cerebrospinal fluid, brain specimens, and cerebral extracellular fluid have all been sources for analysis. Emerging evidence suggests there are distinct proteomic profiles in radiographic TBI subtypes, and that biomarkers may be used to distinguish patients sustaining TBI from healthy controls. Metabolomics may offer a window into the perturbations of ongoing cerebral insults in critically ill patients after severe TBI.

Summary

Emerging MS technologies may offer biomarker discovery and validation opportunities not afforded by conventional means due to its ability to handle the complexities associated with the proteome. While MS techniques are relatively early in development in the neurosciences space, the potential applications to TBI and neurocritical care are likely to accelerate in the coming decade.

Examining four blood biomarkers for the detection of acute intracranial abnormalities following mild traumatic brain injury in older adults

Blood-based biomarkers have been increasingly studied for diagnostic and prognostic purposes in patients with mild traumatic brain injury (MTBI). Biomarker levels in blood have been shown to vary throughout age groups. Our aim was to study four blood biomarkers, glial fibrillary acidic protein (GFAP), ubiquitin C-terminal hydrolase-L1 (UCH-L1), neurofilament light (NF-L), and total tau (t-tau), in older adult patients with MTBI. The study sample was collected in the emergency department in Tampere University Hospital, Finland, between November 2015 and November 2016. All consecutive adult patients with head injury were eligible for inclusion. Serum samples were collected from the enrolled patients, which were frozen and later sent for biomarker analyses. Patients aged 60 years or older with MTBI, head computed tomography (CT) imaging, and available biomarker levels were eligible for this study. A total of 83 patients (mean age = 79.0, SD = 9.58, range = 60-100; 41.0% men) were included in the analysis. GFAP was the only biomarker to show statistically significant differentiation between patients with and without acute head CT abnormalities [U₍₈₃₎ = 280, p < 0.001, r = 0.44; area under the curve (AUC) = 0.79, 95% CI = 0.67-0.91]. The median UCH-L1 values were modestly greater in the abnormal head CT group vs. normal head CT group [U ₍₈₃₎ = 492, p = 0.065, r = 0.20; AUC = 0.63, 95% CI = 0.49-0.77]. Older age was associated with biomarker levels in the normal head CT group, with the most prominent age associations being with NF-L (r = 0.56) and GFAP (r = 0.54). The results support the use of GFAP in detecting abnormal head CT findings in older adults with MTBIs. However, small sample sizes run the risk for producing non-replicable findings that may not generalize to the population and do not translate well to clinical use. Further studies should consider the potential effect of age on biomarker levels when establishing clinical cut-off values for detecting head CT abnormalities.

The evolving role of extracellular vesicles (exosomes) as biomarkers in traumatic brain injury: Clinical perspectives and therapeutic implications

Developing effective disease-modifying therapies for neurodegenerative diseases (NDs) requires reliable diagnostic, disease activity, and progression indicators. While desirable, identifying biomarkers for NDs can be difficult because of the complex cytoarchitecture of the brain and the distinct cell subsets seen in different parts of the central nervous system (CNS). Extracellular vesicles (EVs) are heterogeneous, cell-derived, membrane-bound vesicles involved in the intercellular communication and transport of cell-specific cargos, such as proteins, Ribonucleic acid (RNA), and lipids. The types of EVs include exosomes, microvesicles, and apoptotic bodies based on their size and origin of biogenesis. A growing body of evidence suggests that intercellular communication mediated through EVs is responsible for disseminating important proteins implicated in the progression of traumatic brain injury (TBI) and other NDs. Some studies showed that TBI is a risk factor for different NDs. In terms of therapeutic potential, EVs outperform the alternative synthetic drug delivery methods because they can transverse the blood–brain barrier (BBB) without inducing immunogenicity, impacting neuroinflammation, immunological responses, and prolonged bio-distribution. Furthermore, EV production varies across different cell types and represents intracellular processes. Moreover, proteomic markers, which can represent a variety of pathological processes, such as cellular damage or neuroinflammation, have been frequently studied in neurotrauma research. However, proteomic blood-based biomarkers have short half-lives as they are easily susceptible to degradation. EV-based biomarkers for TBI may represent the complex genetic and neurometabolic abnormalities that occur post-TBI. These biomarkers are not caught by proteomics, less susceptible to degradation and hence more reflective of these modifications (cellular damage and neuroinflammation). In the current narrative and comprehensive review, we sought to discuss the contemporary knowledge and better understanding the EV-based research in TBI, and thus its applications in modern medicine. These applications include the utilization of circulating EVs as biomarkers for diagnosis, developments of EV-based therapies, and managing their associated challenges and opportunities.

Overview of Biofluids and Flow Sensing Techniques Applied in Clinical Practice

This review summarizes the current knowledge on biofluids and the main flow sensing techniques applied in healthcare today. Since the very beginning of the history of medicine, one of the most important assets for evaluating various human diseases has been the analysis of the conditions of the biofluids within the human body. Hence, extensive research on sensors intended to evaluate the flow of many of these fluids in different tissues and organs has been published and, indeed, continues to be published very frequently. The purpose of this review is to provide researchers interested in venturing into biofluid flow sensing with a concise description of the physiological characteristics of the most important body fluids that are likely to be altered by diverse medical conditions. Similarly, a reported compilation of well-established sensors and techniques currently applied in healthcare regarding flow sensing is aimed at serving as a starting point for understanding the theoretical principles involved in the existing methodologies, allowing researchers to determine the most suitable approach to adopt according to their own objectives in this broad field.

Rethinking the initial changes in subarachnoid haemorrhage: Focusing on real-time metabolism during early brain injury

Over the last two decades, neurological researchers have uncovered many pathophysiological mechanisms associated with subarachnoid haemorrhage (SAH), with early brain injury and delayed cerebral ischaemia both contributing to morbidity and mortality. The current dilemma in SAH management inspired us to rethink the nature of the insult in SAH: sudden bleeding into the subarachnoid space and hypoxia due to disturbed cerebral circulation and increased intracranial pressure, generating exogenous stimuli and subsequent pathophysiological processes. Exogenous stimuli are defined as factors which the brain tissue is not normally exposed to when in the healthy state. Intersections of these initial pathogenic factors lead to secondary brain injury with related metabolic changes after SAH. Herein, we summarized the current understanding of efforts to monitor and analyse SAH-related metabolic changes to identify those precise pathophysiological processes and potential therapeutic strategies; in particular, we highlight the restoration of normal cerebrospinal fluid circulation and the normalization of brain-blood interface physiology to alleviate early brain injury and delayed neurological deterioration after SAH.

Biomarkers of Neuroinflammation in Traumatic Brain Injury

Traumatic brain injury (TBI) is characterized by neuroinflammation and structural damage leading to symptoms and altered brain function. Biomarkers are useful in understanding neuroinflammation and correlations with TBI sequalae. The purpose of this paper is to identify and discuss biomarkers of neuroinflammation used to study TBI and its sequalae. A systematic review was conducted using PubMed, CINAHL, Embase, and Web of Science. A total of 350 articles met criteria; 70 used biomarkers. PRISMA criteria were used for Quality Assessment. Articles included reviews (n = 17), case-control (n = 25), cross-sectional (n = 25) studies, and randomized controlled trials (n = 3). Twenty-seven biomarkers were identified, including inflammasomes, cytokines, neuropeptides, complement complexes, miRNA and exosomes, and glial cell-specific proteins. Biomarkers aid in predicting morbidity and mortality and advance our understanding of neuroinflammation in TBI. This systematic review advances our understanding of the neuroinflammatory response to better enable nurses and clinicians to provide informed care of TBI patients.

Subacute cytokine changes after a traumatic brain injury predict chronic brain microstructural alterations on advanced diffusion imaging in the male rat

INTRODUCTION

The process of neuroinflammation occurring after traumatic brain injury (TBI) has received significant attention as a potential prognostic indicator and interventional target to improve patients' outcomes. Indeed, many of the secondary consequences of TBI have been attributed to neuroinflammation and peripheral inflammatory changes. However, inflammatory biomarkers in blood have not yet emerged as a clinical tool for diagnosis of TBI and predicting outcome. The controlled cortical impact model of TBI in the rodent gives reliable readouts of the dynamics of post-TBI neuroinflammation. We now extend this model to include a panel of plasma cytokine biomarkers measured at different time points post-injury, to test the hypothesis that these markers can predict brain microstructural outcome as quantified by advanced diffusion-weighted magnetic resonance imaging (MRI).

METHODS

Fourteen 8-10-week-old male rats were randomly assigned to sham surgery (n = 6) and TBI (n = 8) treatment with a single moderate-severe controlled cortical impact. We collected blood samples for cytokine analysis at days 1, 3, 7, and 60 post-surgery, and carried out standard structural and advanced diffusion-weighted MRI at day 60. We then utilized principal component regression to build an equation predicting different aspects of microstructural changes from the plasma inflammatory marker concentrations measured at different time points.

RESULTS

The TBI group had elevated plasma levels of IL-1β and several neuroprotective cytokines and chemokines (IL-7, CCL3, and GM-CSF) compared to the sham group from days 3 to 60 post-injury. The plasma marker panels obtained at day 7 were significantly associated with the outcome at day 60 of the trans-hemispheric cortical map transfer process that is a frequent finding in unilateral TBI models.

DISCUSSION

These results confirm and extend prior studies showing that day 7 post-injury is a critical temporal window for the reorganisation process following TBI. High plasma level of IL-1β and low plasma levels of the neuroprotective IL-7, CCL3, and GM-CSF of TBI animals at day 60 were associated with greater TBI pathology.

Magnetic Hydrogel for Cartilage Tissue Regeneration as well as a Review on Advantages and Disadvantages of Different Cartilage Repair Strategies

There is a clear clinical need for efficient cartilage healing strategies for treating cartilage defects which burdens millions of patients physically and financially. Different strategies including microfracture technique, osteochondral transfer, and scaffold-based treatments have been suggested for curing cartilage injuries. Although some improvements have been achieved in several facets, current treatments are still less than satisfactory. Recently, different hydrogel-based biomaterials have been suggested as a therapeutic candidate for cartilage tissue regeneration due to their biocompatibility, high water content, and tunability. Specifically, magnetic hydrogels are becoming more attractive due to their smart response to magnetic fields remotely. We seek to outline the context-specific regenerative potential of magnetic hydrogels for cartilage tissue repair. In this review, first, we explained conventional techniques for cartilage repair and then compared them with new scaffold-based approaches. We illustrated various hydrogels used for cartilage regeneration by highlighting the magnetic hydrogels. Also, we gathered in vitro and in vivo studies of how magnetic hydrogels promote chondrogenesis as well as studied the biological mechanism which is responsible for cartilage repair due to the application of magnetic hydrogel.

Blood Biomarkers in Brain Injury Medicine

Purpose of Review

This review seeks to explore blood-based biomarkers with the potential for clinical implementation.

Recent Findings

Emerging non-proteomic biomarkers hold promise for more accurate diagnostic and prognostic capabilities, especially in the subacute to chronic phase of TBI recovery. Further, there is a growing understanding of the overlap between TBI-related and Dementia-related blood biomarkers.

Summary

Given the significant heterogeneity inherent in the clinical diagnosis of Traumatic Brain Injury (TBI), there has been an exponential increase in TBI-related biomarker research over the past two decades. While TBI-related biomarker assessments include both cerebrospinal fluid analysis and advanced neuroimaging modalities, blood-based biomarkers hold the most promise to be non-invasive biomarkers widely available to Brain Injury Medicine clinicians in diverse practice settings. In this article, we review the most relevant blood biomarkers for the field of Brain Injury Medicine, including both proteomic and non-proteomic blood biomarkers, biomarkers of cerebral microvascular injury, and biomarkers that overlap between TBI and Dementia.

S100B, GFAP, UCH-L1 and NSE as predictors of abnormalities on CT imaging following mild traumatic brain injury: a systematic review and meta-analysis of diagnostic test accuracy

Biomarkers such as calcium channel binding protein S100 subunit beta (S100B), glial fibrillary acidic protein (GFAP), ubiquitin c-terminal hydrolase L1 (UCH-L1) and neuron-specific enolase (NSE) have been proposed to aid in screening patients presenting with mild traumatic brain injury (mTBI). As such, we aimed to characterise their accuracy at various thresholds. MEDLINE, SCOPUS and EMBASE were searched, and articles reporting the diagnostic performance of included biomarkers were eligible for inclusion. Risk of bias was assessed using the QUADAS-II criteria. A meta-analysis was performed to assess the predictive value of biomarkers for imaging abnormalities on CT. A total of 2939 citations were identified, and 38 studies were included. Thirty-two studies reported data for S100B. At its conventional threshold of 0.1 μg/L, S100B had a pooled sensitivity of 91% (95%CI 87-94) and a specificity of 30% (95%CI 26-34). The optimal threshold for S100B was 0.72 μg/L, with a sensitivity of 61% (95% CI 50-72) and a specificity of 69% (95% CI 64-74). Nine studies reported data for GFAP. The optimal threshold for GFAP was 626 pg/mL, at which the sensitivity was 71% (95%CI 41-91) and specificity was 71% (95%CI 43-90). Sensitivity of GFAP was maximised at a threshold of 22 pg/mL, which had a sensitivity of 93% (95%CI 73-99) and a specificity of 36% (95%CI 12-68%). Three studies reported data for NSE and two studies for UCH-L1, which precluded meta-analysis. There is evidence to support the use of S100B as a screening tool in mild TBI, and potential advantages to the use of GFAP, which requires further investigation.

Neurofilament light chain in patients with a concussion or head impacts: a systematic review and meta-analysis

PURPOSE

Traumatic brain injury is one of the leading causes of disability worldwide. Mild traumatic brain injury (TBI) is the most common and benign form of TBI, usually referred to by the medical term "concussion". The purpose of our systematic review and meta-analysis was to explore the role of serum and CSF neurofilament light chain (NfL) as a potential biomarker in concussion.

METHODS

We systematically searched PubMed, Web of Science, and Cochrane databases using specific keywords. As the primary outcome, we assessed CSF or serum NfL levels in patients with concussion and head impacts versus controls. The role of NfL in patients with concussion and head impacts compared to healthy controls was also assessed, as well as in sports-related and military-related conditions.

RESULTS

From the initial 617 identified studies, we included 24 studies in our qualitative analysis and 14 studies in our meta-analysis. We found a statistically significant increase of serum NfL in patients suffering from a concussion or head impacts compared to controls (p = 0.0023), highlighting its potential role as a biomarker. From our sub-group analyses, sports-related concussion and mild TBI were mostly correlated with increased serum NfL values. Compared to controls, sports-related concussion was significantly associated with higher NfL levels (p = 0.0015), while no association was noted in patients suffering from head impacts or military-related TBI.

CONCLUSION

Serum NfL levels are higher in all patients suffering from concussion compared to healthy controls. The sports-related concussion was specifically associated with higher levels of NfL. Further studies exploring the use of NfL as a diagnostic and prognostic biomarker in mild TBI and head impacts are needed.